Daksh travels 774 km at 86 km/hr, the next 567 km at 63 km/hr and the next 135 km at 27 km/hr. What is his average speed (in km/hr, rounded off to two decimal places) for the whole journey?​

Correct option is C

Given:

Daksh travels:

774 km at 86 km/hr, 567 km at 63 km/hr, 135 km at 27 km/hr

Formula Used:

Average Speed = $$\frac{\text{Total Distance}}{\text{Total Time}}$$​​

Solution:

Time taken for each part:

​$$\text{Time}_1 = \frac{774}{86} = 9 \text{ hours}$$​​

​$$\text{Time}_2 = \frac{567}{63} = 9 \text{ hours}$$​​

​$$\text{Time}_3 = \frac{135}{27} = 5 \text{ hours}$$​​

Total distance = 774 + 567 + 135 = 1476 km

Total time = 9 + 9 + 5 = 23 hours

Average speed = $$\frac{1476}{23}$$​ = 64.1739 =  64.17 km/hr

Alternate Solution(Exam-hall trick):